upper valve body and shift solenoid replacement

Upper valve body? Are you working on an engine or a transmission?

I believe it is the transmission but my primary goal is to replace a shift solenoid. I noticed a diagram you had posted about this. But I dont really know where to look under the hood

If you're fixing a transmission, you aren't going to find the parts under the hood. shift solenoids are internal to the transmission and unless you are very familiar with transmission work, don't think you should be attempting this yourself.